Direct introduction of a graphite cup into an inductively coupled plasma has been investigated as a method for the determination of sulfur and phosphorus in solutions. The detection limit obtained by measuring the S I 190.027 nm spectral line intensity in an air atmosphere is 1.0 μg/ml. Relative standard deviation at a concentration 100 times the detection limit is about 3%. Thus the results demonstrate the applicability of the present method to practical analysis. A detection limit of 5 ng/ml and a relative standard deviation of 2% are obtained for phosphorus (P I 213.618 and P I 214.911 nm) by optimizing the measurement conditions. The detection limit is close to 15 times that of the conventional method using a nabulizer, and therefore the method is usefull especially for the determination of trace amounts of phosphorus in solutions.
For measurements of luminescence decays, a simple multichannel photon counter has been designed and constructed by use of conventional ECL logic circuits. The photon pulses of luminescence decays are temporarily stored in 64-bit shift registers with a time resolution of 5 or 10 ns and accumulated. The decay curves are efficiently measured in time sharing over the time range from 0 to 81.2 μs when the resolution of 5 ns is selected. The maximum repetition times and the maximum repetition rates are 65536 times and 20 starts/s, respectively. The instrument is aided by a personal computer and much available for measurements of luminescence decays having a decay time of around 100 ns. Also, a wide variety of applications should be found in luminescence spectroscopy. The performance has been shown by measurements of light pulses from a light emitting diode.
The size measurement method for microparticles in liquids using the phase shift of photoacoustic signals theorized in our earlier paper [J. Appl. Phys., 58, 1456 (1985)] was verified using polystyrene turbid solutions. The experimental values for polystyrene microparticles, radii 0.4-5.2 μm, agreed with the theoretical values within the experimental accuracy of ±0.2 deg. The physical meaning of the phase shift was clarified as representing the delay angle of the photoacoustic signal generation determined by the ratio of the heat release time from the microparticles to the modulation period of the excitation beam.Applications of photoacoustic spectroscopy for sizing and determination of microparticles in liquids by proper use of modulation frequency are discussed.